realistically, who could beat him? not only are his in game powers really powerful but if you think about it logically he should be able to do a lot more than just that (he can basically shapeshift into whatever he wants so he can do a lot more than just what they could fit into the game). also, he gets stronger the more biomass he consumes so he could definitely become even more powerful than he ever was in the games if given enough time. also, this guy basically negates all attacks. he survived a nuke because the one little bit of flesh he had left just ate a bunch of pigeons and rats and used their biomass to regenerate his body. his theoretical power cap is insane. imagine if he consumed all the biomass on earth. he would literally become more powerful than a bretheren moon. not only that but he would become basically a god intellect. imagine having the combined neurons of every creature on earth. he is literal lovecraftian god potential.
also prototype 2 isnt canon and he would no diff james heller